Method and apparatus for determining parameters of linear motion in a surgical instrument

Abstract

A surgical instrument and method of controlling the surgical instrument are disclosed. The surgical instrument includes a housing and an elongated shaft that extends distally from the housing and defines a first longitudinal axis. The surgical instrument also includes a firing rod disposed in the elongated shaft and a drive mechanism disposed at least partially within the housing. The drive mechanism mechanically cooperates with the firing rod to move the firing rod. A sensor senses a parameter of light reflected from the surface of the firing rod, which includes markings that change the reflectivity of the firing rod. The measurement unit determines a parameter of the motion of the firing rod, such as the position and speed of the firing rod, based on the sensed parameter of the light reflected from the surface of the firing rod.

What is claimed is: 
     
       1. A method of determining a parameter of motion of a firing rod in a surgical instrument, comprising:
 emitting light on a surface of the firing rod in the surgical instrument, wherein the surface of the firing rod possesses varying reflective properties; 
 sensing a change in a parameter of the light reflected from the surface of the firing rod; and 
 determining a parameter of motion of the firing rod based on the sensed change in the parameter of the light reflected from the surface of the firing rod. 
 
     
     
       2. The method according to  claim 1 , further comprising:
 controlling the motion of the firing rod based on the determined parameter of motion of the firing rod. 
 
     
     
       3. The method according to  claim 2 , wherein the varying reflective properties of the surface of the firing rod are created by a plurality of markings on the surface of the firing rod, and sensing a change in a parameter of the light reflected from the surface of the firing rod comprises counting a number of markings of the plurality of markings on the firing rod that reflect the light. 
     
     
       4. The method according to  claim 2 , wherein sensing a change in a parameter of the light reflected from the surface of the firing rod comprises generating a pulse signal with a parameter that varies with the change in the parameter of the light reflected from the surface of the firing rod, and wherein determining the parameter of motion of the firing rod comprises determining the parameter of motion of the firing rod based on the change in the parameter of the pulse signal. 
     
     
       5. The method according to  claim 1 , wherein the parameter of motion of the firing rod is the position of the firing rod. 
     
     
       6. The method according to  claim 1 , wherein the parameter of motion of the firing rod is the velocity of the firing rod. 
     
     
       7. The method according to  claim 1 , wherein the parameter of the light is phase, frequency, intensity, or polarization. 
     
     
       8. A surgical instrument, comprising:
 a housing; 
 an elongated shaft extending distally from the housing and defining a first longitudinal axis; 
 a firing rod disposed within the elongated shaft, the firing rod having a surface with varying reflective properties; 
 a drive mechanism disposed at least partially within the housing, the drive mechanism in mechanical cooperation with the firing rod; 
 a light emitter that generates and emits light that is directed towards the surface of the firing rod; and 
 a detector that senses a parameter of light reflected from the surface of the firing rod. 
 
     
     
       9. The surgical instrument according to  claim 8 , further comprising:
 a measurement unit that determines a parameter of motion of the firing rod based on the sensed parameter of the light reflected from the surface of the firing rod. 
 
     
     
       10. The surgical instrument according to  claim 9 , wherein the light emitter generates a pulse signal with a parameter that varies with a change in the sensed parameter of the light reflected from the surface of the firing rod, and the measurement unit determines the parameter of motion of the firing rod based on the change in the parameter of the pulse signal. 
     
     
       11. The surgical instrument according to  claim 10 , wherein the parameter of the pulse signal is a frequency of the pulse signal. 
     
     
       12. The surgical instrument according to  claim 10 , wherein the parameter of the pulse signal is a pulse duration of the pulse signal. 
     
     
       13. The surgical instrument according to  claim 9 , wherein the varying reflective properties of the surface of the firing rod are created by a plurality of markings on the surface of the firing rod, and wherein the measurement unit includes a counter that counts a number of markings of the plurality of markings that are exposed to the light emitted from the light emitter based on a change in the sensed parameter of the light reflected from the surface of the firing rod. 
     
     
       14. The surgical instrument according to  claim 9 , wherein the parameter of motion of the firing rod is a position of the firing rod. 
     
     
       15. The surgical instrument according to  claim 9 , wherein the parameter of motion of the firing rod is a velocity of the firing rod. 
     
     
       16. The surgical instrument according to  claim 9 , further comprising:
 a control unit that controls the drive mechanism based on the parameter of motion of the firing rod determined by the measurement unit. 
 
     
     
       17. The surgical instrument according to  claim 8 , wherein the sensed parameter of the light is phase, frequency, intensity, or polarization.